Abstract : A series of poly 2,2'-1,4-phenylene-6,6'-bis 3-phenylquinoxalines (PPQ polymers) DIFFERING IN MOLECULAR WEIGHTS AND POLYMER CHAIN ENDINGS WERE PREPARED, AND THEIR THERMAL DEGRADATION IN AIR AND VACUUM WAS DETERMINED BY ISOTHERMAL WEIGHT LOSS MEASUREMENTS. It was found that the temperature coefficient (an apparent activation energy) of the thermal-oxidative degradation is dependent on the type of polymer chain endings, but not on molecular weight differences. No such chain-end dependency of the temperature coefficient was observed on pyrolysis in vacuum. These differences in apparent activation energies of the degradation of polyphenylquinoxalines in air are attributed to a polymer chain-end unzipping mechanism. (Author-PL)